The invention generally relates to a packer.
A packer is a tool that typically is used in a well for purposes of forming an annular seal between the outer surface of a string (a production tubing, for example) and either the surrounding casing or borehole wall, depending on whether the well is cased. The packer typically includes a ring-like elastomer seal element, which is longitudinally compressed by the thimbles, or gages, of the packer to cause the seal element to radially expand to form the annular seal when the packer is set.
When compressed, the seal element has a tendency to undergo longitudinal extrusion. Because significant longitudinal extrusion may cause a loss of the annular seal (and potentially a catastrophic blowout), the packer typically includes a seal backup system to limit the extent of the longitudinal extrusion. Ideally, a backup system prevents catastrophic blowout of the elastomer seal element at the well pressure; is fully set with a limited setting force; and allows the packer to be unset (for retrievable packers). It may be challenging for a conventional backup system to accomplish these goals, due to ever-increasing well pressure in the environment in which the packer operates.